The bacteriophage fd is being studied by nuclear magnetic resonance (NMR) spectroscopy. Experiments on the isolated major coat protein solubilized with detergents have used 1H NMR at 360 MHz and 13C NMR at 38 MHz to obtain information on the protein in this stable conformation. Solid State 13C and 31P NMR of the intact virus have emphasized the development of cross polarization and magic angle spinning technology for biological problems. Progress is being made on the incorporation of isotopic labels into the virus. Both the 13C and 1H NMR spectra of the major coat protein of fd show that regions of the polypeptide in solution have substantially more motion than typical globular proteins. The alpha carbons of the coat protein show at least two classes of relaxation behavior, which may be indicative of the hydrophobic central region being highly structural but not the hydrophilic ends. The central two tyrosines with pKas of 12.5-12.6 also show substantial involvement in the protein structure. Solid state 31P NMR of fd demonstrate that the single stranded DNA packaged in the virus is very similar chemically and sterically to double stranded DNA, with no evidence of backbone distortion of the DNA. Recently, we have developed solid state NMR technology for observing single 13C resonances from the solid coat protein and the whole virus.